The switching on and off of electrical loads such as commercial lighting, thermal units, or motors drawing currents on the order of hundreds of amperes typically results in arcing between the contacts of the switch, especially when the load is inductive. The arcing both degrades the contact integrity and poses a hot ionized gas safety hazard if severe. Uncontrolled arcing can also cause an explosion if the hot ionized gas touches another current carrying phase or ground. Therefore, such switching functions are usually carried out by means of a switch especially designed to tolerate the arcing and other effects. Such a switch is variously referred to as a "disconnect switch", a "pullout switch", or a "safety switch." Past designs of such switches have usually included a form of knife switch with some arc extinguishing means. Some switches have a knife blade which pivots at one end and breaks from a stationary contact at the other. These are known as "single break" switches. Other switches have an unpivoted blade which engages stationary contacts at both ends. These are known as "double break" switches and have as an advantage over single break switches that the arcing is spread over two sets of contacts. This reduces the linear travel of the contact carrier needed for extinguishing the arc, thereby increasing the breaking speed and reducing damage to the contact integrity. Double break switches can move to a break distance quicker and thus stop arcing faster.
Electrical switches are often provided as gangs of switch units in a known metal enclosure which may include a known snap-action mechanical mechanism for switch operation. The switch units are manufactured with appropriate current and voltage ratings. Multiple switch units are ganged together, either in series or in parallel, to suit the particular application. Switch unit cost and the ease of assembling the switch units in gangs are important considerations to manufacturers of the switch units. Of particular importance in this regard is the flexibility of a switch in its adaptation to various different circuit configurations. It is of course desirable also to minimize any hardware extraneous to a particular application of the switch units.